This invention relates to a process for the hydroformylation of unsaturated hydrocarbons, and more specifically, to a process for hydroformylation in the presence of a catalyst system which is soluble to an amount of at least 2.times.10.sup.-4 mole of the catalyst cation per liter of a liquid mixture of an ethylenically unsaturated compound feed and the hydroformylation product, followed by separating the hydroformylation reaction products from the catalyst system in a solventless evaporative separator.